A 0.45 V low power high PSRR subthreshold CMOS voltage reference

Abstract

Voltage references are broadly used in analog and digital systems to generate a DC voltage independent of process, supply voltage and temperature (PVT) variations. Conventional band gap references (BGR) add the forward bias voltage across a PN junction with a voltage that is proportional to absolute temperature to produce an output that is insensitive to changes in temperature. BGRs generate a nearly temperature independent reference, of about 1.25 V, and therefore they require a higher supply voltage, which might not meet the low voltage constraints for low-power applications such as passive RFID’s, wearable and implantable medical devices. Also, BGRs use resistors that need more area on silicon. One possible solution to meet the low power requirement is to operate MOSFETs in subthreshold region. Most often, forward biased PN-junctions of BGRs are substituted with MOSFETs biased in the subthreshold region and achieves a supply voltage down to 0.6 V.\par This paper presents a sub-1V voltage reference circuit that has only MOS transistors, all working in subthreshold region with a supply voltage down to 0.45 V and a supply current of 1nA at room temperature for ultra-low power applications. The circuit is designed and simulated in 0.13um technology.